1. Field of the Invention
This invention relates generally to electronic circuits and, in particular, to phase locked loop (PLL) circuits used in electronic circuits.
2. Description of the Related Art
PLL circuits are used in many different context. In PLL circuits, an output frequency is locked into a reference frequency. The loop filter of a PLL circuit determines its operating bandwidth. In existing PLL circuits, the bandwidth of the loop filter is constant. Therefore, the operating bandwidth of the PLL circuit is also constant. This limits the usefulness of the PLL circuit.
The present invention addresses this and other disadvantages of existing PLL circuits.